Building up a mean F head

[The Real Roadrunner]

if you like playing drums or kneecapping ppl then hell yeah.

if you were putting his cams in you would have to get some PAR housebricks i mean rods to top the combo off that would slow the response down nicely

[abently]

Much heavier springs, which cause much more wear on the valves and valve seats. Most shim over bucket will run the risk of spitting shims over about 8mm of lift and require much more attention to the wear patterns of the shims over time.

Sorry but that is incorrect.

It is the size of the Shim & size of the bucket which determines how fast you can induce valve lift.

This means you can only get a certain amount of max lift for specific durations.

"Max lift velocity per degree of Crankshaft rotation" (Approx 60degrees of 180degrees of rotation is where Max ramp rates occur)

[abently]

what about accelerated wear? more friction loses due to heavier springs required for valve control?

Friction losses negligible affect on HP, can be offset by lighter Valves and retainers also.

[The Real Roadrunner]

Friction losses negligible affect on HP, can be offset by lighter Valves and retainers also.

in neither of these posts you have answered the responses of high wear rates so obviously you must get your answers from wikipedia where bullshite spreads like wildfire.

[Mr Revhead]

i would have thought that weight has nothing to do with friction.

[Ben Wilson]

You will still have some power losses from the effort of accellerating the valves and retainers.

Generally, if you build the head to take it, lift is gold. Until you get to about 1/3 valve diamater anyway.

Direct acting cams do fairly quickly run out of the amount of lift you can get away with, finger followers, rockers or even pushrods allow for much more extreme ramp rates (and therefore lift) due to their geometry.

Increasing duration will allow you to get more lift without such horrible ramp rates, but a big duration standard lift cam (like Tighe usually sell people), is a horrible thing.

[abently]

in neither of these posts you have answered the responses of high wear rates so obviously you must get your answers from wikipedia where bullshite spreads like wildfire.

Wear and tear on Valve stems and guides is minimal due to Cam over bucket setup.

Yes, there is increased wear on the Camshaft, just use Redline or Motul Oil to keep this to a minimum.

[abently]

Increasing duration will allow you to get more lift without such horrible ramp rates, but a big duration standard lift cam (like Tighe usually sell people), is a horrible thing.

I was wondering why you'se didn't like Tighe..... the race cams 'they designed' for me last year were High-lift (11+ mm) short duration (~274) and about 240 @ 1mm pretty much the opposite.

If you tell them what you want, they'll do it also so its not impossible to get some decent cams out of them.

[abently]

You will still have some power losses from the effort of accellerating the valves and retainers.

Yes that's correct. there's no free lunch.

[Ben Wilson]

I was wondering why you'se didn't like Tighe..... the race cams 'they designed' for me last year were High-lift (11+ mm) short duration (~274) and about 240 @ 1mm pretty much the opposite.

If you tell them what you want, they'll do it also so its not impossible to get some decent cams out of them.

They do some decent grinds, but the advice they give on profiles is horrible. For example, two 4AGs built for rally use; first one wanted a mild rally profile, they sent him 272s with standard lift. The next one wanted something more full on, so they sent him 304s!

[abently]

Sam_Q, as to the exact Head you use or how you Port it, try and look for the straightest Intake Port you can. It only needs to flow 150-155cfm per square In at the choke point. Anymore and any less will hurt velocity.

Here's an interesting link >

http://www.uspto.gov/web/patents/pat...-20070227.html

And an F1 Head >



Enjoy !

[takai]

It is the size of the Shim & size of the bucket which determines how fast you can induce valve lift.

Did you miss the bit where i said MOST?
You started this talk about why factory engines dont use high lift, im pointing out exactly why they dont. Packaging of THEIR shim setups requires ease of change and durability, neither of which you get with high lift high ramprate cams.

It only needs to flow 150-155cfm per square In at the choke point. Anymore and any less will hurt velocity.

Huh, your flow figures are for one specific example, and CANNOT be generalised. Sure it might be fine for a 1.6L with 10.5:1 CR, but for anything other than a specific example it is utter garbage. Also remember your dynamic CR will affect the flow rates you want so that you can optimise the operating band of the engine.

[ed]

what tha...

abently, i suggest toning down the 'absolute-ness' of your posts, and recognise that there are a LOT of smart folks on here who know more than you. you may know a lot (enough to be dangerous anyway) but just slow down or you will be penalised.

[nick.parker]

I have heard of the 1/3 valve diameter is the desirable lift rule of thumb. But is there much benefit in going for larger diameter valves, such that the diameter is larger than 3 times the lift? I have heard hypotheses that low end torque loss is minimal and top end better for the same camshafts...sounds reasonable to me....

[oldcorollas]

it all depends on what is limiting the flow into the cylinder. if the valve or valve lift is not the restriction, then it won't help...